Aluminum alloys have more reduced corrosion resistance than that of pure aluminum due to their alloy elements. Therefore, an oxidation film needs to be electrochemically formed on a surface of the aluminum alloys to enhance surface wear resistance. Herein, a method for forming the oxidation film is referred to as an anodizing method.
The anodizing method is a compound word of anode and oxidizing and is a method for forming an aluminum film (Al2O3) by conducting electricity in an electrolytic solution using an aluminum alloy as an anode and oxidizing an aluminum surface by oxygen generated from the anode.
The aluminum film has excellent durability and corrosion resistance, and a micro columnar cell thereof ranges from several nm to several μm growing thereon to form a micro porous surface.
General anodization is performed using an electrolyte in which a concentration of sulfuric acid ranges from 15 to 20 wt %.
Referring to FIG. 1, aluminum alloys for casting include a large amount of Si for improvement of fluidity. In the alloys including the large amount of Si, the Si is not dissolved during an anodizing process, and therefore remains in place and lumps of non-anodized Si form an island to cause cracks on a surface of an oxidation film, thereby reducing corrosion resistance.
The contents described as the related art have been provided only for assisting in the understanding for the background of the present disclosure and should not be considered as corresponding to the related art known to those skilled in the art.